Aldosterone is a steroid hormone secreted in the adrenal cortex. In primary cells of the distal tubules and collecting ducts of the kidney, aldosterone binding to the mineralocorticoid receptor (MR) results in the retention of sodium and water and excretion of potassium, which in turn leads to increased blood pressure. Aldosterone also causes inflammation that leads to fibrosis and remodeling in the heart, vasculature and kidney. This inflammation may proceed by MR-dependent as well as MR-independent mechanisms (Gilbert, K. C. et al., Curr. Opin. Endocrinol. Diabetes Obes., vol. 17, 2010, pp. 199-204).
Mineralocorticoid receptor antagonists (MRAs), such as spironolactone and eplerenone, have been used previously to block the effects of aldosterone binding to MR. When given in addition to standard therapies such as angiotensin-converting enzyme (ACE) inhibitors and loop diuretics, the nonselective MRA spironolactone and the selective MRA eplerenone significantly reduced morbidity and mortality in patients with heart failure or myocardial infarction (Pitt, B. et al., New Engl. J. Med., vol. 341, 1999, pp. 709-717; Pitt, B. et al., New Engl. J. Med., vol. 348, 2003, pp. 1382-1390). However, the nonselective MRA spironolactone can also bind to and act at other steroid receptors, and as a consequence its use is associated with sexual side effects such as gynecomastia, dysmenorrhoea and impotence (Pitt, B. et al., New Engl. J. Med., vol. 341, 1999, pp. 709-717; MacFadyen, R. J. et al., Cardiovasc. Res., vol. 35, 1997, pp 30-34; Soberman, J. E. et al., Curr. Hypertens. Rep., vol. 2, 2000, pp 451-456). Additionally, both spironolactone and eplerenone are known to cause elevated plasma postassium levels (hyperkalemia) and elevated aldosterone levels.
An alternative method of blocking the effects of aldosterone is to inhibit its biosynthesis. CYP11B2 is a mitochondrial cytochrome P450 enzyme that catalyzes the final oxidative steps in the conversion of 11-deoxycorticosterone, a steroidal precursor, to aldosterone (Kawamoto, T. et al., Proc. Natl. Acad. Sci. USA, vol. 89, 1992, pp. 1458-1462). Compounds that inhibit CYP11B2 should thus inhibit the formation of aldosterone. Such compounds, particularly those of nonsteroidal structure, should provide the beneficial effects of MRAs, without the adverse effects derived from steroid receptor binding or MR-independent inflammatory pathways.
CYP11B1 is a related enzyme that catalyzes the formation of glucocorticoids, such as cortisol, an important regulator of glucose metabolism. Because human CYP11B2 and CYP11B1 are greater than 93% homologous, it is possible for nonselective compounds to inhibit both enzymes (Kawamoto, T. et al., Proc. Natl. Acad. Sci. USA, vol. 89, 1992, pp 1458-1462; Taymans, S. E. et al., J. Clin. Endocrinol. Metab., vol. 83, 1998, pp 1033-1036). It would be preferable, however, for therapeutic agents to selectively inhibit CYP11B2 and the formation of aldosterone with diminished inhibition of, or affect on, CYP11B1 and the production of cortisol.
WO 2009/135651 to Elexopharm describes 6-pyridin-3yl-3,4,-dihydro-1H-quinolin-2-one derivatives as being CYP11B2 inhibitors. Two compounds described therein are lactam derivatives of the formula:
Structurally similar lactam and thiolactam compounds are disclosed by Lucas et al., J. Med. Chem. 2008, 51, 8077-8087; those compounds are said to be potential inhibitors of CYP11B2. Lucas et al. in J. Med. Chem. 2011, 54, 2307-2309 describes certain pyridine substituted 3,4-dihydro-1H-quinolin-2-ones as being highly potent as selective inhibitors of CYP11B2 and WO 2012/012478 to Merck describes benzimidazole analogues as having the ability to CYP11B2. An abstract of a dissertation reports that a series of novel heterocyclic-substituted 4,5-dihydro-[1,2,4]triazolo[4,3a]quinolones was evaluated for its aldosterone synthase activity; one of the compounds is reported as exhibiting excellent selectivity of CYP11B2 over CYP11B1. WO 2012/148808 to Merck and ElexoPharm also discloses tricyclic triazole compounds that possess aldosterone synthase activity.
WO 1999/40094 to Bayer AG describes oxazolidinone derivatives with azol-containing tricycles as possessing antimicrobial activity. An example of one of the compounds disclosed therein is:

The compounds of the invention provide an alternative to previous treatments for elevated aldosterone levels and inhibit CYP11B2.